The Effects of MCT Oil and Glucose Polymer Ingestion on Endurance Exercise

by

Brenda Lou Orr

Thesis submitted to the Faculty of the

Virginia Polytechnic Institute and State University

in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

APPROVED:

Eric Clegg

Forrest Thye

in

Education.·

Janet L. Walberg

William G. Herbert

July, 1984 Blacksburg, Virginia

The Effects of MCT oil and A Glucose Polymer on

Endurance Performance

by

Brenda Lou Orr

(Abstract)

Seven experienced male bicyclists performed four

endurance test rides at 70% ( ± 5) V02 max on a

bicycle at 90 RPM over a four week period.

stationary

Subjects

consumed a high carbohydrate diet (70%) for two days prior

to each test ride.

During each test, heart rate (HR), rate of perceived

exertion (RPE), V02 , respiratory exchange ratio (R), serum

free fatty acid (FFA) and serum glucose levels were

measured. One of the four test treatments was randomly

administered, in a single-blind design, at 5, 25, and 40

minutes into each exercise bout. The control trial (CTR)

included 50 gelatin capsules· containing water, and a

lemonade beverage (150 ml each) sweetened with an artificial

sweetener (Saccharin). The test mixtures were made up in

the same manner as the control with the addition of one of

the test substances: 1) MCT oil (M), 2) glucose polymer (P)

(Polycose, Ross Laboratories), 3) MCT plus glucose polymer

(MP). Depending on the treatment used, MCT oil-containing

capsules replaced water-capsules and/or Polycose was

dissolved in the lemonade beverage. Total caloric intake of

each trial, except control, was 360 calories.

No significant difference was found between mean time

to exhaustion for the four treatments. No significant

difference was noted between treatments for R, V02 , and HR

responses (p < 0.05). Significantly greater RPE values were

found over the first 60 minutes of exercise for the Control

treatment as

(p < 0.05).

compared

Repeated

to the

measures

other three treatments

ANOVA showed that

significantly higher serum glucose values existed for

treatment P as compared to Mand also significantly higher

serum FFA values existed for treatment Mas compared to both

P and MCT oil with Polycose (MP) over the first 60 minutes

of exercise (p < 0.05}.

Although the combination of MCT oil and Polycose would

th~oretically enhance endurance performance due to an

increased supply of both FFA and glucose available for

muscular metabolism, this dietary treatment was ineffective

in prolonging exercise time.

Index terms: MCT oil; Glucose Polymer (Polycose);

endurance performance

Acknowledgements

The time has finally come for me to express my own

appreciation for the many people who have had a supporting

part in the completion of this study. This I extend to the

following:

Dr. Janet Walberg,

aspect of

for the major support she gave in every

this study, but especially for her

individualized interest and concern expressed, and for

the useful comments in all the revisions made

throughout the entirety of this study.

Dr. Eric Clegg, for the generosity of his time and knowledge

given in performing the FFA assays, and for his own

professional critique.

Dr. William Herbert,

manuscript.

Dr. Forrest Thye,

for his critique of the overall

for his technical assistance and

meticulous review of the manuscript.

To my team of seven subjects, for their diligence to their

commitment, and who, without their support, this study

could not have been performed: David Andrews, Rick

Armstrong, Jeff Bowermaster, Chris Gibson, Keith

Helmink, Paul Hollandsworth, and Bob Tuscan.

iv

Barb Redican, for her nursing skills that allowed for the

technical procedures of this study and also for her

invaluable personal support through out the testing.

Ross Laboratories, whose funding allowed for the undertaking

of this study.

Houston Couch, for his generosity with his computer and lab.

Virginia Polytechnic Institute and State University' s

Department of Vet Medicine, for opening up their lab

and personnel to me to use for many technical

procedures.

Edward Okie, for giving generously many, many hours of

computer assistance and support.

To the "family" at Dayspring, who have supported me in

prayer, and otherwise, over the years required for this

completion.

And, of course, to the Lord, God, the ultimate Author of

this paper, whose support was and is endless in all

ways (Col. 3: 23 - 24). Amen.

V

TABLE OF CONTENTS

ABSTRACT ........................................ .

ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .

LI ST OF TABLES .................................. .

LI ST OF FIGURES ................................. .

Page ii

iv

vii

viii

CHAPTER l: INTRODUCTION......................... 1

Statement of the Problem............. 3 Research Hypothesis.................. 3 Delimitations and Limitations........ 4 Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . 5 Significance of the Study............ 7 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

CHAPTER 2: REVIEW OF THE LITERATURE............. 9

Mechanisms of Fatigue During Endur-ance exercise........................ 9 Glucose Utilization During Exercise.. 13 FFA: Energy Source During Exercise.. 18 MCT Oil: Absorption and Metabolism.. 23 Gastric Emptying Time: How It Is Affected By Nutrients And Exercise... 28 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 0

CHAPTER 3: THE EFFECTS OF MCT OIL AND GLUCOSE POLYMER INGESTION ON ENDURANCE PERFORMANCE. . . . . . . . . . . . . . . . . . . . . . . . . . 32

Introduction......................... 34 Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 6 Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Discussion........................... 43 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . 48

CHAPTER 4 : SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Implications. . . . . . . . . . . . . . . . . . . . . . . . . 65 Recommendations. . . . . . . . . . . . . . . . . . . . . . 66

REFERENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

APPENDICES ........ ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

vi

List Of Tables

Page Table 1. Characteristics of Subjects ................... 53

Table 2. Statistical Summary of Analysis of Variance with Repeated Measures for FFA, Glucose, HR, R, RPE, and VO~ through minute 60 of exercise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Table 3. Mean and S.E. values for heart rate and respi-ratory ratios through out exercise ............ 55

Table 4. Mean and S.E. values for serum metabolites (glucose and FFA) and results of one-way Anova ......................................... 56

vii

List Of Figures

Figure 1. Mean time to exhaustion for treatments MCT oil (M), Polycose (P), MCT oil with

Page

Polycose (MP), and Control (CTR) ............ 57

Figure 2. Mean V02 , R, and HR values for treat-ments MCT oil(•), glucose polymer (o), MCT oil and glucose polymer(•), and Control (•) during exercise ................• 58

Figure 3. Mean serum glucose and free fatty acid values for treatments MCT oil (•), glu-cose polymer (o), MCT oil and glucose polymer(•), and Control (•), during, at exhaustion, and 30 minutes post ex-ercise...................................... 59

viii

Chapter 1

Introduction

Endurance performance is limited by an individuals'

tolerance to fatigue. Fatigue· has been related to several

factors including muscle glycogen deletion and hypoglycemia.

Enhancement of athletic performance via nutritional

ergogenic

(Costill,

aides has

Dalsky, &

been

Fink,

the subject of

1978). Glucose

many studies

administered

during exercise has been shown to delay fatigue possibly by

replenishing depleted muscular endogenous supplies or by

delaying hypoglycemia. However, if this same treatment is

given prior to exercise, a hypoglycemic reaction at the

beginning of exercise has been observed. This results in an

impaired endurance performance (Foster, Costill, & Fink,

1979). Results of studies examining the effect of caffeine

on performance indicate an increased plasma free fatty acid

(FFA) level occurs suggesting an increase in muscular lipid

catabolism. This allows for a decrease in carbohydrate

utilization (Costill et al, 1978).

In a study by Rennie (Rennie, Winder, & Holloszy,

1976), control-exercised rats had muscle glycogen values of

43.4 micro moles of glucose/gm at rest. After 30 minutes of

exercise, the glycogen level was depleted to 11. 7 micro

mole. Rats treated with a fatty meal had muscle glycogen

values of 45.5 at rest and 21.6 micro mole after exercise.

1

Co still, ( Costill,

1977) showed that

2

Coyle, Dal sky, Evans,

an elevation of FFA

Fink, &: Hoopes,

following heparin

injections lowered the rate of muscle glycogen depletion by

40% as compared to the control.

These comparisons show a muscle glycogen sparing action

when FFA are elevated during exercise. This glycogen

sparing action results in prolonged endurance exercise

performance (Costill et al, 1977). Thus, accumulation and

utilization of plasma substrates, other than glucose seem to

prolong endurance performance, primarily by sparing muscle

and liver glycogen stores.

MCT oil, comprised of Octanoic acid (71%), Decanoic

acid {23%) and a mixture of longer and shorter chain length

fatty acids { 6%), is a lipid that is rapidly absorbed and

metabolized.

portal vein

MCT is quickly and directly absorbed into the

as glycerol and fatty acids. It is then

transported to the liver where it is quickly metabolized to

ketone bodies {KB), CO2 , and acetate (Greenberger &:

Skillman, 1969). As KB concentration increases, muscular

glycolysis is inhibited (Randle, Garland, Hales, &:

Newsholme, 1963). In addition, KB are metabolized as an

energy source by the central nervous system (CNS) , and

therefore further spares glucose. Thus, MCT oil

administered during endurance performance could potentially

spare muscle glycogen. This hypothesis has not been tested.

3

The effect of MCT oil mixed with cereal and milk on

metabolism during a 60 minute exercise bout was studied by

Ivy (Ivy, Costill, Fink, & Maglischo, 1980). Since this

study was of fixed duration (60 minutes), and since MCT was

given in a mixture of other foods, the effect of MCT alone

on endurance performance was not determined. It is the

intent of this study to test the effects of feeding MCT oil

alone or in combination with a carbohydrate source during

exercise, on metabolism and endurance performance.

Statement of the problem

If glycogen depletion is a major cause of fatigue

during exercise, methods which will prolong the availability

of muscle glycogen stores may delay fatigue.

Caffeine and heparin administered during exercise,

exhibit a glycogen sparing action through their stimulation

of plasma FFA and prolong aerobic exercise time. However,

the effects of a direct source of FFA and ketone bodies has

not been studied during endurance performance. With MCT oil

providing a source of FFA' s that are quickly absorbed and

metabolized to KB, it was the intent of this study to

determine if there were any adverse reactions to MCT oil

given during exercise and to determine if this lipid source

provides an alternative source of energy which could be

utilized in preference to glycogen stores to prolong

endurance performance.

Research Hypotheses

4

Null hYPothesis: There will be no significant difference in

time-to-exhaustion between endurance tests in which a

water, glucose polymer, MCT oil, or combined glucose

polymer-MCT oil beverage is administered.

Null HYPothesis: Serum glucose and serum FFA levels, heart

rate, R value, and V02 will not change over time during

exercise for any of the treatments.

Null HYPothesis: The four treatments given during exercise

will not affect the serum glucose, serum FFA, heart

rate, R value, or V02 response during exercise

Delimitations and Limitations

To insure the absence of variance between and within

subjects' results, the following measures were

undertaken:

I. Delimitations

A. All subjects were males, under 35 years old.

B. All subjects were required to have exercised on a

bike a minimum of SO miles per week for six weeks

prior to the study, and for the entire duration of

the study.

C. All subjects were screened for diabetes rnelli tus,

celiac sprue, and liver diseases, due to possible

complications with MCT oil ingestions in these

conditions.

5

D. All subjects were deleted from the study if they 1)

smoked, 2) had low tolerance to needle/IV catheter

insertion, 3) were not willing to adhere to a

prescribed diet for two days prior to each test

ride.

II. Limitations

A. Small sample size (N=7).

B. Individual subject compliance to prescribed diet and

overnight fast prior to each test ride was

voluntary. Some intersubject variance from this

prescription may have existed.

C. Subject acceptance and/or tolerance to the beverages

administered may affect tolerance to exercise.

D. True exhaustion had to be assumed for each test,

therefore

exhaustion.

Definitions

results may not reflect absolute

Endurance tests: tests performed at 70% V02 max on a

bicycle ergometer to exhaustion at 90 RPM's.

Fluid replacement beverage: a beverage administered during

the course of strenuous exercise to replace elements

depleted during endurance exercise, such as body water,

glucose, and fatty acids, and electrolytes.

6

Free fatty acids (FFA): metabolically, the most active of

the plasma lipids comprising less than 5% of the total

fatty acids present in plasma; they are an easi,ly

metabolized lipid energy source used for muscular

contraction.

Glycogen, muscle:

muscle cell.

storage form of carbohydrates within the

Ketone bodies: a collective term for acetoacetic acid and

its derivative B-hydroxybutyric acid and acetone;

recognized as products of fatty acids and certain amino

acid catabolism formed in the liver and used by most

tissues, including the brain, as fuels and reduces the

need of glucose.

Maximum oxygen uptake (V0 2 ): a functional measure of ones'

physical fitness status; it is the largest amount of 0 2

one can consume per minute.

Medium chain triglycerides (MCT): one form of a neutral

lipid, triglycerides,

molecules with a chain

which contain

length varying

fatty acid

from six to

twelve carbon atoms, approximately 75% of the fatty

acids are C:8, 23% are C: 10, 1% are C: 12, and 1% are

C:6.

Polycose: a powdered-form, glucose polymer product

manufactured by Ross Laboratories.

Rate of perceived exertion

made by each subject,

( RPE) : subjective measurements

reflecting their own perceived

7

amount of exertion during the endurance tests, based on

Borgs' scale of numbers from 6 to 20 in a quanto-format

with descriptive words printed beside every other

number, ranging from "very, very light" at 117 11 to

"very, very hard" at 1119 11 •·

Respiratory quotient (RQ): the ratio of the volume of CO2

produced to the 02 consumed at the cellular level; it

is 1.0 - 0.9 for carbohydrate metabolism, 0.9 - 0.8 for

a mixed diet, and 0.8 - 0.7 for fat metabolism. This

parameter gives an indication of fuel utilization.

Significance of the study

If endurance performance can be enhanced via use of a

readily available lipid energy source, i.e., MCT oil, alone

or with a carbohydrate source, athletes may consider the use

of this substance to enhance exercise performance.

Summary

Endurance athletes are continuously searching for ways

to increase their athletic performance. Some measures

employed have included glucose ingestion during exercise,

caffeine ingestion, and heparin administration. These were

tested to determine their effect on metabolism and ability

to spare glycogen during performance.

An increase in endogenous glucose, and an increase in

plasma FFA were observed to enhance endurance performance in

8

these studies. However, a readily available source of FFA

and KB, MCT oil has not been studied for its effects on

endurance performance. It was the purpose of this study to

determine the benefits of administering MCT oil alone and

with a glucose polymer during exercise. Specifically, to

observe the effects of MCT oil on plasma FFA and glucose and

its influence on endurance performance.

Chapter II

REVIEW OF THE LITERATURE

Introduction

Many factors contribute to the scope of this study,

therefore, the following areas will be reviewed: 1.)

mechanisms of fatigue during endurance exercise, 2.)

glucose: its utilization during exercise, 3.) FFA: an

energy source during exercise, 4.) MCT oil absorption and

metabolism, and, 5.) gastric emptying time: how it is

affected by nutrients and exercise.

MECHANISMS OF FATIGUE DURING ENDURANCE EXERCISE

Depletion of muscle glycogen, exercise-induced

hypoglycemia, plus water and electrolyte loss in sweat are

the major factors that cause fatigue and impaired

performance during prolonged exercise (Costill et al, 1977;

Fordtran & Saltin, 1967; Hickson, Rennie, Conlee, Winder, &

Holloszy, 1977). This can be characterized by a.) a rapid

increase of blood lactate levels, b.) concomittant rise in

RQ above 1.0, C.) a heart rate approaching max heart rate,

d.) a drop in blood sugar levels, and e.) a rise in the

blood FFA/glucose ratio (Rodahl, Miller, & Issekutz 1964;

Christensen & Hansen, 1939). Other factors that may

contribute to fatigue are enzymatic, hormonal, and nerve

conduction changes (Costill, Sparks, Gregor, & Turner,

1971).

9

10

Carbohydrate is used to supply energy primarily during

high intensity exercise. The main source of carbohydrate is

the local glycogen stored in the specific muscle tissue.

After depletion of these glycogen stores the muscle depends

on blood glucose replenished by liver gluconeogenesis.

After severe drain on these carbohydrate sources, exercise

above a certain intensity is no longer possible (Bjorntorp,

1983). A decrease in glycogen content as determined by

needle biopsy, in the working muscles was shown to be well

correlated to total carbohydrate utilization during work

periods in a study performed by Bergstrom (Bergstrom,

Hermansen, Hultman, & Saltin, 1967). The subjects exercised

on a stationary bike at 75% V0 2 max to exhaustion. He, as

well as Costill (Costil), Bennett, Branam, & Eddy, 1973)

concluded that the glycogen content was a determining factor

in the capacity to perform long-term heavy exercise.

Costill (Costill et al, 1977) showed that an elevation

of plasma FFA decreased the rate of muscle glycogen

depletion by 40%. This increased FFA oxidation produced an

accumulation of citrate in the heart and skeletal muscles,

and therefore lirni ted the rate of glycolysis and pyruvate

oxidation. Due to this increased reliance on fat metabolism

and therefore a sparing of muscle glycogen, there is an

enhanced capacity for endurance exercise (Ivy et al, 1979).

Holloszy (Holloszy & Booth, 1976) and Hickson (Hickson

et al, 1977) also indicated that in trained muscles, there

11

is an increased fat oxidation and increased capacity for

glycogen synthesis, both resulting in a slower depletion of

glycogen stores. Thus, allowing for an increase in exercise

time to exhaustion.

Severe hypoglycemia has been observed during prolonged

heavy exercise and may limit performance (Bergstrom &

Hultman, 1972). However, its limitation during exercise is

on the central nervous system (CNS) and not on the working

muscles. Yet, this limitation on the CNS will influence

coordinated muscular performance (Asmussen, 1965).

To avoid glycogen depletion resulting in hypoglycemia

the glycogen stores should be well filled prior to the day

of hard exercise. This can be achieved by giving a high

carbohydrate diet for several days before the event

(Bergstrom et al, 1972). Also, hypoglycemia may be delayed

by increasing the availability of KB' s, which are also a

good alternative substrate for the CNS (Hickson et al,

1977).

However, high fat diets consumed prior to exercise were

not shown to increase endurance performance (Asmussen, '65).

This could be due to the higher oxygen cost for exercise

when mainly fat is metabolized, ie, a greater 0 2 uptake is

required of subjects to metabolize the predominant fat

substrate. Also KB' s formed 9-uring fat combustion, which

cause undesireable acidosis in endurance exercise, and the

depletion of body glycogen stores as a result of this diet,

contribute to poor endurance performance (Asmussen, 1965).

12

Costill (Costill et al, 1971) demonstrated in a bicycle

ergometry study that, at 80% max, the glycogen content of

the medial quadriceps femoris was nearly exhausted in about

one hour of exercise. This type of exercise tends to

isolate metabolic demands to a ·relatively small muscle mass.

Localized muscular stress can also be a factor in

endurance exercise. On a bicycle this is evidenced by

higher perceptions of exertion due to greater muscle force

required to overcome the resistance when slow pedalling

speeds, as compared to fast speeds, are maintained (Pandolf

& Noble, 1973). Muscular and joint discomfort realized by

the rider would contribute to this sensation of stress.

Also, Pandolf suggested that the anaerobic metabolism and

therefore lactic acid production would contribute to a

higher RPE value.

Endurance performance on a bicycle ergometer can be

enhanced by using a high pedalling rate. Pandolf (Pandolf &

Noble, 1973) suggests using 60-80 RPM, rather than the usual

50-60 RPM, as the higher pedalling speeds enable one to

better evaluate the subjects' cardio-respiratory fitness as

a limiting factor to performance rather than localized

muscular fatigue. At slower pedalling rates, the resistance

becomes greater due to more sustained contraction and

increased muscular i schemia with high ·1actate levels. As a

result, cyclist naturally prefer a high pedalling speed for

cycling competition. However, Gollnick (Gollnick, Piehl, &

13

Saltin, 1974) showed that varying the pedalling rate had no

effect on patterns of glycogen depletion in the m..;.scle

fiber.

The muscle fiber type present in exercising muscles

will also play an important role in delaying fatigue during

prolonged endurance exercise. Red muscle fiber (slow

twitch) are able to utilize an increased supply of FFA for

energy, inhibiting carbohydrate utilization and therefore

sparing muscle glycogen stores. The white muscle fibers

have a low capacity to oxidize and utilize FFA for energy

and will deplete muscle glycogen stores more quickly. This

may explain part of the effect of training on fuel

utilization. For example, Karlsson (Karlsson, Nordes, &

Sal tin, 1974) proposed that the enhanced fat oxidation and

the decreased carbohydrate oxidation in trained subjects are

brought about by an increased recruitment of red muscle

fibers. This is indicated by the decrease in the RQ value

observed in the trained subjects.

GLUCOSE UTILIZATION DURING EXERCISE

Carbohydrate ingestion during exercise may offset

fatigue, caused by a decreased rate of muscle glycogen

utilization during events of long duration (ie, greater than

or equal to 60 minutes), (Costill et al, 1973 and Ahlberg &

Felig, 1976). This is due to the maintenance of blood

glucose by exogenous ingestion during exercise.

14

Costill has shown that ingestion of glucose 30 to 45

minutes prior to exercise produces hypoglycemia, depresses

the mobilization of serum FFA, and thereby reduces the

exercise time to exhaustion. Ivy (Ivy et al, 1980)

indicated that insulin levels are also elevated dramatically

when a glucose feeding is given immediately prior to

exercise. It was therefore shown that the glucose feedings

prior to exercise increased the rate of carbohydrate

oxidation yet impeded the mobilization of FFA. This

decreased the exercise time to exhaustion (Ivy et al,1980).

However, if glucose is consumed during exercise,

elevated blood glucose levels are maintained. The rate of

fatigue was reduced in the latter stages of an exercise

bout, enabling an increase in total work production.

Gluconeogenesis in the liver from glycerol, lactate,

alanine, and KB' s may also delay symptoms of hypoglycemia

(Hickson et al, 1977; Neely & Morgan,1974). Yet, the time

of total work production was not increased. In contrast,

Hickson (Hickson et al, 1977) showed that if glucose was

given at the time of fatigue during endurance exercise, the

subjects could continue the exercise bout for a significant

amount of time; the ingested glucose was utilized by the

brain (CNS) as adequate FFA were being metabolized by

exercising muscles,

prolonged.

and therefore exercise time was

15

Costill (Costill et al, 1973) has shown that glucose

ingested during exercise does not contribute much ( about

5.4%) to carbohydrate oxidation. Wahren (1977) also

indicated that glucose administration during strenuous

exercise does not significantly decrease muscle glycogen

consumption. Yet, another study by Ivy (Ivy et al, 1979)

involved the ingestion of about 90 grams of a glucose

polymer (Polycose) during the first 90 minutes of endurance

exercise on a bicycle ergometer at 80 RPM. It was shown to

have no effect on total work production of V02 , yet it was

effective in decreasing the rate of fatigue over the last 30

minutes of cycling, and therefore may have been effective in

sparing muscle glycogen.

However, since the hepatic contribution to blood

glucose is reduced following the ingestion of glucose during

exercise, it is possible that such feedings may prevent

liver glycogen depletion during prolonged severe exercise.

Current findings suggest that gluconeogenesis from

endogenous precursors is inhibited when glucose feedings are

given during exercise (Ahlberg and Felig, '76). Therefore,

an increase in exercise time to exhaustion was observed.

A possible mechanism for the beneficial effect of

carbohydrate feedings during exercise as opposed to effects

if given before exercise may be the contrasting effects on

plasma insulin. For example, in a study by Ahlberg,

(Ahlborg & Felig, 1977) it was shown that glucose ingested

16

prior to mild exercise ( 30% max V02 ) resulted in

hyperinsulinemia and hyperglycemia. However, Bonen has

shown that glucose ingestion during intense exercise failed

to increase glucose and insulin concentration(Bonen,

Malcohlm, & Kilgour, 1981). This contrasts with Ahlborgs'

study where a rise in serum insulin was observed when

glucose was ingested during mild exercise which enhanced the

exercise-stimulated glucose uptake (Koivisto, Karonen &

Nikkila, 1981). The increase in carbohydrate utilization

by exercising legs and inhibition of lipolysis after glucose

feedings could be attributed to an increase in arterial

glucose, elevation in plasma insulin, or both (Ahlberg et

al, 1976).

The

studies

difference

appears to

in insulin responses in these

be related to differences

two

in

norepinephrine levels provoked by different intensities of

exercise, ie, intense being 80% V02 max, mild being less

than or equal to 65% V02 max (Bonen et al, 1981). When

glucose is ingested during mild exercise, there is a rise in

serum insulin, during intense exercise, the norepinephrine

response inhibits insulin release from the pancreas (Bonen

et al, 1981). Henter and Sukkar (Costill et al, 1973)

reported evidence to suggest that increased utilization of

glucose during muscular work is not dependent upon insulin.

Costill (Costill et al, 1977) also presented strong

evidence in- a study that ingested glucose appeared in the

17

blood within 5 to 7 minutes after ingestion, and that it

was the primary carbohydrate source during intense exercise.

Since intense exercise (80%) normally relies extensively on

carbohydrate metabolism, glucose ingestion prior to

exercise, utilizing glycogen-depleted subjects, is

qualitatively and quantitatively more important than its

ingestion before mild (40% max V02 ) exercise (Bonen et al,

1981).

Bergstrom (Bergstrom et al 1972), described the general

breakdown of glycogen during submax exercise as the

following 1.) initial rapid decrease due to stimulation

by the initial muscle contraction, adrenaline release, and

possibly a local decrease of 0 2 pressure; 2.) second phase

notes an adaptation of circulation to work load and changes

in enzymatic activities which result in a decreased rate of

glycogen consumption, and, 3.) final phase, in which there

is a relative lack of glycogen and the muscle partially

compensates for this by an increased uptake of blood glucose

and an increase in lipid metabolism.

The repeated muscle contraction is associated with a

marked increase in muscle cell permeability to glucose.

Increased transport of glucose into the cell followed by

conversion to glucose-6-phosphate, which would inhibit

glycogenolysis (Baldwin, Reitman, Terjung, Winder, &

Hollosky, 1973). So, it would seem important to maintain

blood glucose as well to achieve a high level of glycogen

18

storage prior to an exhaustive bout of endurance exercise to

delay fatigue (Bergstrom, 1972).

In a study by Astrand, (1969), three different types of

diets were compared for exercise time to exhaustion on a

bicycle ergometer. Subjects performed only 57 minutes while

on a high fatjhigh protein diet, for 114 minutes with a

mixed diet, and for 167 minutes on a high-carbohydrate diet,

therefore supporting the importance of glycogen utilization

in endurance exercise.

Another important factor related to glycogen sparing is

the level of training sustained by individual subjects.

Karlsson

there is

(Karlsson et al,

lower glycogen

1974),

depletion

showed in a study that

and lower RQ values

during exercise performed at the same 0 2 uptake level for

each subject. This points to a reduced oxidative use of

carbohydrate after training, possibly brought on by an

increased recruitment of red muscle fibers (Karlsson &

Saltin, 1971; 1974). Therefore, after training, there is an

increase in oxidative enzymes and an increase in the

capacity to oxidize fatty acids. Hollosky, (Hollosky et al,

1976) indicated that there is also an increased capacity for

glycogen synthesis in trained muscles.

FFA: ENERGY SOURCE DURING EXERCISE

At a given metabolic rate,

c;,ppears to be · determined by

the rate of FFA oxidation

2 factors: 1) the

concentration of fatty acids, (ie, substrate availability),

19

and 2) the capacity of the tissue to oxidize fat, due to

adaptation in muscle mitochondria and an increas~ in their

enzymes involved with FFA oxidation (Oscai & Palmer, 1983).

Therefore, the availability of FFA to the mitochondria is

perhaps the rate-limiting factor for FFA oxidation at any

given work rate (Hollosky et al, 1976).

Ivy (Ivy et al, 1980) indicated that an increased

insulin level during exercise, causes a preferential

oxidation of carbohydrate even when FFA and ketone bodies

are present in elevated amounts. Insulin also acts by

decreasing the rate of release of FFA.

In endurance ex,ercise, there tends to be a fall in

circulating

glucagon.

lipolysis

insulin, with a

This allows for

(Ahlberg et al,

resultant rise

a progressive

1976). These

in plasma

increase of

changes are

influenced by norepinephrine production. An increase of

norepinephrine in the blood and adipose tissue, increases

the lipolytic action in adipose tissue, and possibly also

limits insulin release from the pancreas.

With the increased metabolic rate and increased

norepinephrine production, plus decreased insulin levels,

the energy stores of adipose tissue and muscle become

available for metabolism, and a shift towards fat

utilization will occur (Paul, 1970).

An increased mobilization of FFA during exercise can

result from hydrolysis of triglycerides in adipose tissue,

20

as indicated by a rise in plasma glycerol concentrations

(Havel, Naimark, Borchgrevink, 1963). This can be an

important source of energy for muscular contraction (Young,

Shapira, Forrest, Adachi, Lim, & Pelligra, 1967). Terjung

(Terjung, Mackie, Dudley, & Kaciuba-Useilko, 1983) showed

that, in fed, exercising animals, there was a direct uptake

of TG-derived FFA that could be used for beta-oxidation.

These FFA repr~sented a large source of energy substrate in

a post-prandial state. It was this source of lipid, that

when experimentally controlled, appeared to enhance exercise

performance and spare muscle glycogen (Terjung et al, 1983).

During prolonged exercise, mobilization of FFA's from

adipose tissue increases gradually. This results in a

decreased plasma concentration initially, followed by the

gradual increase, and ending with a peak concentration

immediately post exercise. (Bjorntorp, 1983). It is the

trained subjects, again, who have a greater ability to

release FFA from adipose tissue which enhances proportions

of energy that can be produced thru fat metabolism (Lewis,

1973). Trained endurance athletes will be able to derive

more of their energy from fat and less from carbohydrate

than untrained individuals with less formation of lactic

acid (Hickson et al, 1977; Hollosky et al, 1976). This

adaptation induced in skeletal muscles could be responsible

for delaying muscle glycogen depletion and therefore

prolonging endurance exercise in trained individuals. In

21

addition, the trained person will produce less lactate at a

given workload than an untrained person. H:i.gh levels of

blood lactate may interfere with release of FFA (Rodahl et

al, 1964 and Lewis &: Gutin, 1973). Thus, the trained

individual is again at an advantage for fat utilization

during exercise.

Bonen (Bonen et al, 1981) demonstrated that during

intense exercise ( about 80% V02 max), causing lactic acid

production, fat metabolism was decreased even when FFA

concentrations remained elevated; carbohydrate metabolism

was then preferred. This is in agreement with a study by

Paul (1970) in which it was shown that as long as the 0 2

supply was adequate, without a rise in lactate, the FFA

turnover and oxidation rate increased in a way that the

percentage of total energy derived from FFA oxidation would

be equal at higher workloads. But, as lactate rose with

increasing workloads, the FFA turnover rose insufficiently.

Even though the turnover percentage was large, the amount of

energy derived from plasma FFA oxidation was considerably

less at this time (Paul, 1970). This indicated that the FFA

turnover and oxidation rates were dependent not only on

plasma FFA levels, but also on the adequacy of the 0 2 supply

to the working muscle and adipose tissue.

In a study by Costill et al (1977) 7 males exercised on

a treadmill at 70% V02 max. Plasma FFA were elevated with

heparin (2,000 units), decreasing muscle glycogen depletion

22

by 40%, as compared to controls. Apparently this was due to

the inhibitory effect of citrate on phosphofructokinase,

therefore limiting the rate of glycolysis.

Diet, prior to or during an endurance event will also

affect the rate of FFA mobilization and utilization.

Issekutz (Issekutz, Birkhead, & Rodahl, 1963) suggested

that it was the actual carbohydrate intake rather than the

amount of fat in the diet that was a determining factor of

whether fatty acids or glucose would be primarily utilized

during exercise.

FFA metabolism will be decreased when glucose is given

prior to or during strenuous exercise (80% V02 ), even though

the FFA concentration may remain elevated (Bonen et

al,1981).

In a study by Christensen (Christensen & Karlsson,

1939), subjects consumed a specified diet for several days

prior to a bicycle exercise bout at 1,080 KPM/min. One plan

utilized a high fat, low carbohydrate ( 5%) diet, which

resulted in a decreased work RQ. The second plan, consisted

of a high carbohydrate (90%), low fat diet, and had opposite

effects (Christensen & Karlsson, 1939). The R value is

related mainly to: 1.) diet of subjects, 2.) intensity of

work, and 3.) duration of work (Asmussen, 1965).. Also,

when serum FFA levels are increased prior to exercise, as

following an overnight fast, there is a marked increase in

FFA oxidation (Ivy, 1980).

23

In a study by Ivy (Ivy et al, 1980) subjects exercised

at 70% V02 max.

inhibited if

It was indicated that FFA metabolism was

source,

would

subjects

one hour prior

be diminished

consumed cereal, a carbohydrate

to exercise. Also that lipolysis

if carbohydrate was taken during

exercise.

Other researchers also indicated that decreased FFA

concentration after glucose ingestion during exercise may

result in decreased FFA utilization. (Koivisto et al, 1981;

Havel et al, 1963; Ahlborg et al, 1976; Bellet, Kershbaum, &

Finck, 1968). Following a glucose feeding during exercise,

the carbohydrate inhibits mobilization of FFA's from adipose

tissue

burn.

and therefore skeletal muscles receive less to

This could be attributable to an elevation in

arterial glucose or an increase in plasma insulin, or both

(Ahlborg et al, 1976; Foster et al, 1979).

MCT OIL: ABSORPTION AND METABOLISM

MCT oil is a form of neutral lipid triglycerides that

contains fatty acid molecules of 6 to 12 carbon atoms in

length (Greenberger et al, 1969); Holt, 1971). 71% is

octanoic acid (C:8), 23% is decanoic acid (C:10), (Ivy et

al,1981).

MCT oil requires less pancreatic lipase of bile salt

for digestion than does long chain triglycerides (LCT).

They are more rapidly and efficiently absorbed from

24

intestine than are LCT after digestion and intestinal

absorption (Guy, 1981; Baba, Bracco, & Hashim, 1982). They

may be absorbed intact by the small intestine and are

completely hydrolysed in intestinal mucousal cells. Gastric

lipase might hydrolyze ingested MCT. Such gastric

hydrolysis might contribute to its efficient absorption

(Cohen, 1970).

Trioctanoin, in the form of MCT oil, is rapidly

hydrolzed by pancratic lipase to octanoic acid. These fatty

acids that are derived from MCT are absorbed and transported

via the portal vein as the fatty acid directly to the liver;

they are not deposited in adipose tissue, (Guy, 1981;

Greenberger et al, 1969; Holt, 1967). It has also been

shown that the fatty acids of MCT do not appear in the

plasma after oral administration.

Hashim (1966) reported that, after oral intake of MCT

oil, 90% was present in the FFA form in the portal vein

indicating mucousal hydrolysis of MCT.

Once these medium chain fatty acids (MCFA) reach the

liver they are rapidly metabolized and oxidized extensively

into CO2 , water, acetate, and ketones (Guy, 1981; Baba,

1982; Greenberger et al, 1969). The MCFA not catabolized

are converted to long chain fatty acids (LCFA) and

esterified to LCT. The rapid conversion of MCFA to CO2 has

been utilized to estimate intestinal absorption indirectly.

In normal human subjects following oral administration of

25

C-14 trioctanoin, 15 to 20% of the dose was recovered in

expired air within 50 minutes (Greenberger et al, 1969).

Hashim (1966) reported 15% recovery of C-14 MCT as CO2

within the first 20 to 60 minutes.

Hyperketonemia, which results from hepatic metabolism

of MCFA, causes an increase in insulin secretion. Tamir

(Tamir, Grant, Fosbrooke, Segall, & Lloyd, 1968) showed that

insulin output from the pancreas in rats, can be directly

stimulated by octanoic acid. An increased insulin secretion

following MCT ingestion may lower glucose levels.

Increasing the concentration of FFA's impairs glucose

tolerance causing hypoglycemia, due to reduced hepatic

glucose release (Greenberger et al, 1969).

In a ·study by Tantibhedhyangkul, (Tan~ibhedhyangkul,

Hashim, & Vanitallie, 1967), 7 normal subjects were given 1

gm/ kg body weight of MCT oil inducing mild hyperketonemia.

At the height of MCT-induced hyperketonemia, glucose

tolerance was not impaired. However, octanoate-induced

hyperketonemia appears to depress glycolysis in the liver

resulting in hypoglycemia and a lower rate of FFA

synthesis. This may further enhance ketogenesis. This

resulting hyperketonemia may promote insulin secretion, and

under this condition, an improvement in glucose tolerance to

an administered glucose load will be noted. Pi-Sunyer

observed a decrease in glucose transport and utilization in

heart and skeletal muscle in the presence of K.B. 's (Pi-

Sunyer, Hashim, & Vanitallie, 1969).

26

Newsolme, et al, (Newsolme, Randle, & Manchester, 1962)

proposed this is due to an inhibition of glucose transport

and phosphofructokinase (PFK), by muscular K.B. catabolism.

That is, K.B.-mediated depression of glycolysis is similar

to the inhibitory effect of ·FFA oxidation on glycolysis

mediated by PFK inhibition (Randle, et al, '63). K.B.'s

formed after MCT oil ingestion can also serve as an energy

source to the CNS (Owen Morgan, & Kemp, 1967), and therefore

this could be another means to spare muscle glycogen.

Linscheer (Linscheer, Chalmers, & Slone, 1967) and

Tarnir (1968) showed that glucose given along with MCT would

increase serum insulin levels more than if glucose was given

alone. If MCT is being administered, and a sudden glucose

load is given, the rate of glucose disappearance may be

improved above normal rates (Greenberger, 1969).

When carbohydrates are given during the ketogenic phase

following MCT ingestion, ketogenesis may be inhibited. This

suggests that the TCA cycle is not functioning at a maximal

rate when challenged with MCT, but can be accelerated by

adding substrate, therefore decreasing the ketone formation

(Freund & Weinsier, 1966). Yet, Schwabe (Schwabe, Bennett,

& Bowman, 1964) has shown that prompt oxidation of MCT was

not substantially inhibited by moderate doses of glucose.

MCFA are metabolized as quickly as glucose (Ivy, 1980).

Other results following MCT oil ingestion include

nausea, vomiting, abdominal pain, and diarrhea. These may

27

be related to the rapid hydrolysis and resulting high

concentration of FFA in the stomach :md small intestine

(Holt, 1967 and 1971).

Holt (1971) has shown that 40 to 50 grams of MCT can be

tolerated in patients throughout the day. However, Ivy (Ivy

et al, 1980) gave subjects 50 to 60 gm of MCT which resulted

in 100% of subjects with cramping and diarrhea. Then, 30 gm

was given, resulting in only about 10% of subjects

experiencing any negative effects from MCT ingestion.

Ivy performed a 60 minute test with 10 subjects, at 70%

V0 2 , on a bicycle ergometer (80 RPM} and treadmill. This

study determined the effect of 30 gm of MCT oil mixed with

cereal on metabolism during endurance exercise. Ketone body

concentration increased with MCT ingestion. Ketone bodies

are readily metabolized by skeletal muscle (Little, Goto, &

Spitzer, 1970). Since ketone body oxidation is primarily a

function of plasma concentration (Harper, Rodwell, & Mayes,

1977) ketones were likely serving as energy substrates in

the muscles after MCT ingestion. The blood concentration of

K.B. is probably the determining factor for the rate of

oxidation in the CNS (Hultman & Nilsson, 1975).

Of interest is Bassenges' observation (in Little et al,

1970} that when ketones were infused into dogs, an increase

in RQ was seen along with a drop in the removal of FFA.

However, RQ results in Ivys' study (1980) indicated that the

carbohydrate utilization was the same in the MCT and cereal

28

test as well as the cereal test alone. Since RQ was used

only to indicate percent carbohydrate and fat oxidized,

ketone body formation and oxidation was not included in this

measure. Therefore, the conclusion determined by Ivy, (Ivy

et al, 1980) that ketone bodies did not contribute to energy

needs of exercise may not hold true.

GASTRIC EMPTYING TIME: HOW IT IS AFFECTED BY NUTRIENTS AND

EXERCISE

Many studies have shown that volume, osmotic pressure,

and chemical composition of a test meal influence gastric

emptying (Costill & Saltin, 1974; Hunt & Knox, 1968). The

rate at which the stomach empties is strongly influenced by

the chemical and physical properties of the chyme entering

the duodenum (Costill et al, 1974).

Hunt has suggested that duodenal receptors monitor the

osmolari ty of gastric emptying and by a feedback loop,

influence the rate of gastric emptying (Hunt et al, 1968).

A saline solution affected gastric emptying only in terms of

volume infused: as nutrient was added, the emptying slowed

down. However, identification of either the receptors or

pathways, neural or humor al, by which the receptors might

exert their control is lacking.

Also, volume, chemical composition ,and osmotic

pressure are major determinants for gastric emptying

(Davenport, 1969). Osmotic pressure effects the rate of

29

gastric emptying via the enterogastric reflex; the higher

the pressure, the slower the emptying rate. Of the 3 major

foodstuffs, fat has the greatest effect on delaying gastric

emptying, carbohydrates empty the quickest.

Painful levels of ingragastric pressure inhibit gastric

motility, as volumes greater than 600 to 750 ml reduce the

rate of gastric emptying (Costill et al, 1974). In

particular, it is important to minimize the sugar content of

fluids administered during high intensity exercise (Greater

than 70% VO, max). Otherwise, the inhibitory effect of both

exercise and glucose content on gastric emptying may combine

to block gastric emptying. Costill (Costill, 1974) stated

that, in general, exercise has no effect on emptying until

work intensity is greater than 70% max.

In another study by Co still, it was shown that the

osmotic effect of glucose only delayed gastric emptying when

the concentration exceeded 139mM. A glucose solution of

greater than 139 mM emptied from the stomach in a continuous

flow (21 ml/min.) soon after ingestion. Addition of even 5

gm/100 ml, glucose in water, caused a marked inhibition of

gastric emptying (Costill, 1973).

When a 125 ml "test meal" of MCT oil was administered

to healthy, fasted subjects, at least 6 hours was required

for complete gastric emptying to occur (Pirk & Skala, 1970).

The ingestion of 1 gm/kg body weight of MCT oil increased

octanoic acid from 0% to 50% within 30 minutes, and peaked

at 57.7% 90 minutes after ingestion (Tamir et al, 1968).

30

Another study has shown that approximately 15% of an

orally or intravenously administered C-14 labeled MCT was

recovered as C0 2 -14 within the first 20 to 60 minutes

(Schwabe et al, 1964; Hashim, 1966; Greenberger et al,1969).

McHugh (McHugh Sc Moran, 1979) ·indicated that MCT oil meals

at O. 5 calories/ml, emptied at the same rate as glucose.

Fatty acids of less than 10 carbon atoms are relatively

ineffective in slowing gastric emptying time (Hunt, 1968).

Three isocaloric meals, of 150 mls at 0.5 calories/ml, were

compared in their gastric emptying time. Casein

hydrolysate, an MCT oil suspension, and glucose resulted

with superimposable regression lines. I socaloric loads of

these 3 nutrients, as stated, emptied from the stomach at

the same rate.

Intensity of exercise

Costill (Costill Sc Saltin,

effects gastric emptying als·o.

1974) has shown that exercise

(cycling) has little effect on gastric emptying at workloads

requiring

prolonged

less than 70% of one's V0 2

endurance did not cause a

emptying time.

max. In addition,

change in gastric

In summary, endurance exercise perf orrnance has been

found to improve when serum glucose or FFA levels are

increased via glucose ingestion during exercise or caffeine

ingestion and heparin injections, respectively. Total

exercise time was increased with glucose ingestion during

exercise (Ivy et al, 1983). FFA were utilized more

31

extensively for energy, therefore possibly sparing muscle

glycogen, when increased with caffeine and heparin, given

prior to exercise (Costill et al, 1971 and Ivy et al, 1979).

However, the effects of administering MCT oil alone or with

Polycose during endurance exercise has not been determined

previously. Therefore, this study was performed to

determine the benefits, if any, of administering these

treatments during prolonged exercise.

Chapter III

JOURNAL MANUSCRIPT

32

The Effects of MCT Oil and Glucose Polymer Ingestion on Endurance Exercise

Brenda L. Orr, Janet L. Walberg, Eric Clegg, William G. Herbert, and

Forrest Thye

Brenda L. Orr and Janet L. Walberg Human Performance Laboratory Department HPER VPI & SU Blacksburg, VA 24061 703-961-6561

33

Introduction

Fatigue during endurance performance is associated with

depletion of muscle glycogen stores and hypoglycemia

(Costill et al, 1977; Fordtran et al, 1967; Hickson et al,

1977). Glucose, when ingested· prior to exercise, has been

shown to cause a hypoglycemic reaction during exercise, and

therefore reduced time-to-exhaustion. The glucose ingestion

increases serum glucose levels, with increased insulin

levels, which allow for increased peripheral glucose

utilization with impeded mobilization of free fatty acids

(FFA). Therefore muscle glycogen depletion is increased

while liver glucose output is diminished (Bergstrom &

Hultman, 1972).

However, if carbohydrate is given during exercise, the

muscle glycogen utilization rate may be lowered during

endurance exercise ( equal to or greater than 60 minutes),

due to maintenance of blood glucose levels by the

exogenously supplied glucose (Costill et al, 1973; Ahlborg

et al, 1976). Ivy et al. (1983) have shown that time to

exhaustion can be significantly increased when carbohydrate

(Polycose, 120 gms) is given during exercise. Costill

(1977) has shown that with heparin (2,000 units) muscle

glycogen can also be spared by raising serum free fatty acid

(FFA) levels, and therefore utilization, during exercise,

enhancing the capacity for more endurance exercise (Ivy et

al, 1979). Caffeine ingestion and heparin injections have

34

35

both been used to increase serum FE'A levels and have been

shown to cause a muscle glycogen sparing effect and

therefore enhanced endurance performance (Costill et al,

1978 and 1977).

Trioctinoin, in the form of medium chain triglyceride

oil (MCT oil), is a lipid containing fatty acid molecules

with a chain length varying from six to twelve carbon atoms.

It is a rapidly absorbed and metabolized source of lipid and

could be another means to spare muscle glycogen when

ingested prior to or during endurance exercise. Following

the ingestion of MCT oil, the resulting medium chain fatty

acids (MCFA) are quickly transported to the liver for

metabolism and oxidation into CO2 , water, acetate, and

ketone bodies, resulting in hyperketonemia (Owen, 1967).

This results in increased insulin secretions which may lower

glucose levels. Yet, in the presence of ketone bodies,

glucose transport and utilization has been shown to

decrease. These ketone bodies formed after MCT oil

ingestion can serve as an energy source to the central

nervous system,

et al, 1967).

therefore sparing glucose utilization (Owen

Thus, MCT oil ingestion could theoretically

spare muscle glycogen during endurance performance.

MCT oil given alone and with a glucose polymer

(Polycose), during endurance exercise has not been studied.

Since FE'A oxidation is mainly a function of plasma

concentration for these substrates, and since the proportion

36

of lipids given to

increased FFA levels,

energy metabolism is greater with

carbohydrate utilization should be

reduced, causing a glycogen sparing action. Since MCT may

increase hepatic FFA synthesis and reduce ketone clearance

(Greenberger, 1969) it was the intent of this study to

determine if beneficial effects may have been attributable

to MCT oil alone and in combination with glucose, during

endurance exercise, on total exercise time and on serum FFA

and glucose.

Methods

Seven experienced male bicyclists were chosen as

subjects for this study. Each biked at least 50 miles/week

for six weeks prior to the study, and continued this level

of exercise during the entire testing period. (Table 1).

All subjects were between the ages of 18 and 31, and

were required to give informed consent. Subjects were

disqualified from the study if they had 1) diabetes

melli tus, 2) cirrhosis

inflamatory bowel disease

1967), 4) ever smoked

or other liver diseases, 3)

(Greenberger et al, 1969; Holt,

tobacco products, and 5) were

intolerant to intravenous catheter insertion and usage.

Subjects were requested not to consume alcohol or

caffeine for 24 hours prior to the endurance rides and not

to exercise strenuously for the same period. The initial

meeting included measurements of resting EKG, maximum oxygen

consumption on a bicycle ergometer, exercising EKG and blood

37

pressure, and analysis of a previously completed three-day

diet record to determine average calorie intake for each

subject. A pre-test trial ride was us.ed to familiarize each

subject with the experimental procedures and to determine if

the designated work rate was appropriate. Each subject was

scheduled to participate in one experiment per week on the

same day of the week and at the same time of day.

All subjects consumed a 500 calorie meal of fixed

nutrient composition (70% carbohydrate, 18% fat, 12%

protein) by 8: 00 p. m. the evening before each endurance

bicycle ride and arrived to the lab after an overnight fast

and without breakfast. Upon arrival to the lab, initial dry

weight was obtained. An indwelling catheter was inserted in

a forearm vein (cephalic or basilic) by a registered nurse.

The vein was kept open during exercise by a continuous drip

of sterile saline at an infusion rate of 20 - 40 cc/hour.

Subjects consumed one of four capsule and beverage

mixtures, as a single-blind design. The control trial

included gelatin capsules containing water, and a lemonade

beverage (150 ml each) sweetened with saccharin. The test

mixtures were made up in the same manner as the control with

the addition of one of the test substances: 1) MCT oil (40

gms), 2) glucose polymer (Polycose powder, Ross

Laboratories) { 94. 7 gms), 3) MCT oi 1 plus glucose polymer

(20.0 gm MCT oil plus 47.7 gm Polycose). MCT oil replaced

water in all the capsules during the MCT oil-containing test

38

rides while MCT oil capsules replaced half of the water

capsules in the MCT-Polycose test rides. Polycose powder

was dissolved in the lemonade in the MCT-Polycose and the

Polycose only rides.

The first capsule/beverage (150ml) consumption occurred

after 5 minutes of the endurance bout for a total caloric

intake of 180 calories. The second and third capsule/

beverage (150 ml each) treatment was consumed at 25 minutes

and 40 minutes of exercise, respectively, for a caloric

intake of 90 calories each. Calories from the combined MCT

oil and Polycose solution contributed equally from both

nutrients. Therefore, total calories consumed during all

exercise bouts, except the control, were 360 calories each.

Immediately prior to each exercise bout, resting EKG,

and initial blood samples (5 ml) were obtained. Seat height

was adjusted to a determined level specific for each subject

throughout the testing period. A fan was placed about 3

feet in front of the subjects during each test ride to

minimize thermal stress.

the cadence at 90 RPMs'.

A metronome was used to control

During the 70% (±5) V02 max exercise rides, rate of

perceived exertion (RPE: Borg scale), V02 , respiratory

exchange ratio (R), and heart rate (HR) were measured every

10 minutes until exhaustion. Exhaustion was determined as

that point when subjects were unable to maintain pedalling

speed. Blood samples were obtained at 15 minutes into

39

exercise, every 30 minutes during exercise, at exhaustion,

and after 30 minutes of recovery. Total volume blood

collected per trial per subject was approximately 30 - 35

mls.

Blood samples were ·immediately separated by

centrifugation. Serum was frozen for later analysis for

glucose and FFA. Serum glucose (rng/dl) was analyzed using

the glucose oxidase method (#510 Sigma Glucose Enzymatic

Colorimetric Assay Kit). Serum FFA (mM) concentration was

measured using a colorimetric procedure (Costill et al,

1980).

Expired 0 2 and CO2 were analyzed during the bicycle

tests using the Hewlett Packard 4730A Digital Pneumotach to

determine V02 and R values. Calibration of the analyzers

was performed prior to and periodically during each test

ride using 0 2 and CO2 reference gases. Heart rate

measurements were taken during exercise using a single lead

EKG.

One-way ANOVA was performed on HR, R, V02 , FFA, and

glucose at their specific measured intervals through minute

60 of exercis·e, and at exhaustion for all four treatments;

this was also performed on serum FFA and glucose at time-to-

exhaustion and 30 minutes post-exercise. Repeated measures

ANOVA was performed on RPE plus all the above dependent

variables through 60 minutes of exercise. Duncan Multiple

Range test was used to determine which treatments were found

40

to be significantly different from the others. The level of

significance accepted wasp< 0.05.

Results

There was no significant difference noted between mean

time to exhaustion for the four treatments. However, as

shown in Figure 1 subjects tended to have the longest

exercise time when receiving Polycose (P) and the shortest

when consuming MCT oil (M) alone (Appendix 0). MCT oil and

Polycose combined (MP) and the control (CTR) resulted in a

similar intermediate exercise time (Appendix 0). Most

subjects reported "nausea" to be the main reason for

terminating exercise during treatment M. Only a few

subjects reported this for treatment MP and none for the P

or CTR treatments. Almost all subjects reported that

boredom,• a time factor in their own schedule, or being

"saddle sore", were the main reasons for terminating

exercise during treatment P and CTR. This would indicate P

provided an energy supply that was better tolerated, by the

gastrointestinal system, than the other treatments.

The subjects had similar R, V02 , and HR responses to

the four treatments through minute 60 (p < 0.05) (Table 2;

Figure 2). Based on the respiratory exchange ratio (R),

carbohydrate (CHO) and fat oxidation were essentially the

same for all treatments through minute 80. The R value for

41

P and CTR trials continued to rise up to exhaustion while R

for the MP and M treatments showed a slight decline until

exhaustion (Figure 2). MCT oil given alone during exercise

or in combination with carbohydrate appeared to enhance fat

oxidation during latter stages of prolonged exercise while

provision of carbohydrate substrate alone as Polycose

increased the CHO metabolized for energy.

Oxygen uptake (V0 2 ) was essentially the same through

out exercise, for all four treatments. However, V02 from

minute 60 to exhaustion during treatment M tended to exhibit

a higher response than the other three treatments. This

indicated a greater 0 2 supply was necessary to oxidize and

metabolize the increased levels of FFA resulting from

treatment M, which was consistent with the slightly lower R

values for M.

The heart rate data (Figure 2) showed there was a

normal rise in HR during exercise over time fo~ all

treatments as exercise commenced. However, there was no

significant difference found between any of the treatments

during exercise (Table 2).

As expected, rate of perceived exertion (RPE) (Figure

2), also indicated a progressive rise over time. RPE values

were only recorded throughout the first 60 minutes of

exercise, and then at random for the remainder of the test

ride. Treatment CTR data indicated there was a

significantly greater perceived effort through the first 60

42

minutes of exercise than the other three treatments (p <

0.05) (Table 2). The least effort was reported during the

MP trial. One subject even reported a drop in perceived

exertion during treatment P, from 1114" at minute 60 to 1112"

at minute 90 on the Borg scale indicating less perceived

effort during the last 50 minutes of his exercise bout.

ANOVA for repeated measures showed that significantly

higher glucose values for treatment P existed over the first

60 minutes of exercise compared to treatment M (p < 0.05)

( Figure 3) (Appendix R). Treatment P caused a noticeable

rise in glucose from time Oto 15 minutes. A slight drop in

serum glucose was noted for both MP and CTR trials at minute

15 followed by a rise up to minute 30, at which time there

was a progressive drop on through exhaustion. MCT oil

consumption tended to result in the lowest levels of blood

glucose (Figure 3). All four treatments consistently

displayed a drop in mean serum glucose values during the

last 30 minutes of exercise, indicating a gradual depletion

in carbohydrate supplies. Serum glucose in the MP trial was

found to be significantly higher than CTR and MCT oil alone

at 30 minutes post exercise (p < 0.05).

ANOVA for repeated measures indicated that serum FFA

values for treatment M were significantly higher than both P

and MP up through 60 minutes of exercise (p < 0.05)

(Appendix R). Also, there was a significant time effect on

FFA levels during this time peri·od, again, treatment M

43

allowed for the highest values (Figure 3). The divergence

in serum FFA values, as noted in Figure 3, began at minute

30 of exercise. At this time CTR rose from 0.4 mM FFA to an

average end point of 0.94 mM at exhaustion. P, providing no

exogenous fat, showed a consistently lower concentration of

FFA throughout exercise. MCT provided the greatest FFA

supply, up to minute 90, which was found to be significantly

greater than treatment Pat minute 60 only (p < 0.05).

The blood analysis was found to be consistent with the

R data in suggesting a greater supply and utilization of FFA

by subjects during exercise when MCT oil was ingested and an

enhanced carbohydrate utilization when Polycose was

consumed.

Discussion

Numerous studies have indicated that depletion of

endogenous carbohydrate stores is a limiting factor in

endurance exercise, and that reducing the rate of glycogen

utilization should improve endurance performance (Costill et

al, 1977; Hickson et al, 1977; Rennie et al, 1976). Seiple

et al (1983) have shown that, when compared to free glucose,

a 5% carbohydrate solution with Polycose resulted in 69%

more fluid and 33% more carbohydrate being sent to the small

intestines after 30 minutes of ingestion delaying endogenous

glycogen depletion during exercise. Also, it has been shown

that with an inctea.;;ed level of serum free fatty acids,

there was an increased rate of muscular lipid metabolism

44

therefore reducing muscle glycogen utilization in exercising

skeletal muscle (Costill et al, 1977; Issekutz et al, 1965).

The use of MCT oil (M) treatment alone, and Polycose

(P) treatment alone, in the present study, caused a

significant increase in plasma FFA and glucose,

respectively. However, mean time to exhaustion was not

found to be significantly different between MCT oil-

containing trials, Polycose trials, or the control. In

fact, treatment M, was found to hinder exercise performance

due to the nausea that occurred after ingestion of 40 g of

MCT oil. A study by Ivy (1980) indicated that even 30 gms

of MCT oil when ingested prior to exercise would cause

abdominal cramping and diarrhea. Even the MP trial,

al though containing only half the amount of MCT oi 1 as

treatment M, resulted with 3 of 7 subjects complaining of

nausea.

Carbohydrate given during· exercise, in the form of

Polycose, seemed to result in the longest exercise bouts

(not significant). However, no significant difference in

time to exhaustion was noted between treatments. A study by

Ivy et al. ( 1979), showed that when 90 gm of Polycose was

given during a two hour endurance bike ride, work production

increased above what was found during the first 10 minutes

of exercise. This was possibly due to the elevated supply

of blood glucose made available for utilization at that

time. This report suggested that Polycose might allow an

45

increased exercise time to exhaustion in endurance work. In

fact, a later report ( Ivy et al, 1983) showed that when

Polycose (120 gms) was given during exercise, time to

exhaustion was significantly increased by 11.5% as compared

to the control group.

The downward trend in R values for the Mand MP trials

could have been indicative of the increasing FFA utilization

as a result of the MCT oil ingestion. In studies by Costill

et al. (1971) and Ivy et al. (1979) FFA levels were

increased by caffeine ingestion and heparin injections prior

to exercise. The R data in both studies also demonstrated

an increase in fat oxidation with a reduced rate of

carbohydrate oxidation , indicating an enhanced utilization

of FFA by exercising muscles. Therefore, since serum FFA

levels were elevated by the ingestion of MCT oil in the

present study, this could indicate an enhanced sparing of

glycogen stores, as FFA contributed progressively more to

the energy for work. However,the present study was not able

to determine this due to the occurrence of nausea. Polycose

seemed to provide an exogenous carbohydrate supply that was

relied on more extensively than fat, especially during the

latter part of the exercise bouts, as noted by the

increasing R value throughout exercise. Alternately, the

rise in R values at the end of exercise for both P and CTR

might also have been influenced by respiratory compensation

secondary to increased lactate production as fatigue was

approached (Rodahl et al, 1964).

46

A similar pattern of average heart rate values was

noted over the four treatments indicating there was no

significant difference in cardiovascular stress as a result

of the nutrient treatments. However, RPE results did

indicate a significant difference in effort sensations

resulting from the various treatments. The greatest mean

RPE values reported were for the CTR trials, followed by the

MCT oil trials. The sensation of nausea reported by most

subjects after ingesting MCT oil, was possibly the main

contributing factor affecting the rate of perceived effort

reported. The lowest values for mean perceived effort,

noted in both trials containing Polycose (P and MP), again

support its beneficial metabolic effect in the final phases

of endurance exercise when given during exercise.

The mean serum glucose level generally decreased after

90 minutes of exercise and was even found to reach

hypoglycemic levels at exhaustion for one subject during the

CTR trials. Again, this could be the primary cause for

exhaustion during this treatment (Ivy et al, 1979). The

significantly lower glucose values found during the MCT oil

treatment, as compared to Polycose (p < 0. OS), may be

related to several factors. MCT oil ingestion has been

shown to reduce liver glucose output unrelated to increased

insulin secretion or enhanced glucose utilization

(Tantbhedhyankul et al, 1967). The hyperketonemia noted

after MCT oil ingestion may promote insulin secretion,

47

resulting in diminished glucose output by the liver

(Tantbhedhyankul et al, 1967).

When carbohydrate (Polycose) was given with MCT oil

(MP), glucose tolerance was not impaired but possibly

enhanced in its uptake (Tantibhedgyankul et al, 1967). This

seemed to be indicated by the glucose levels noted in the

present study for the MP trials. When given alone Polycose

tended to maintain slightly higher serum glucose levels

during exercise.

MCT oil was found to provide the greatest mean FFA

supply. Since the level of plasma FFA levels directly

affects the rate of FFA oxidation (Ivy et al, 1979), it can

be assumed that MCT oil provided an increased supply of FFA

for energy during this endurance exercise bout. However

when carbohydrate was given with the MCT oil (MP trial) this

effect on serum FFA levels and thus muscle fuel utilization

was possibly reduced. Ivy et al. (1980) also found that

when MCT oil was given to subjects with carbohydrate one

hour prior to exercise, FFA metabolism was inhibited.

Polycose ingestion alone, during exercise, caused the

largest reduction in amount of serum FFA' s available for

metabolism up through minute 90 of trial P. Ivy (1979) has

indicated that when carbohydrate (90 g of glucose polymer)

was given during exercise, lipolysis was diminished. This

could be due to an increase in arterial glucose and an

increase in plasma insulin, or both (Miller, 1984). This

48

was in contrast to a study by Costill et al. ( 1973), in

which glucose given (31.8 gm) at 30 minutes into exercise,

followed by 60 minutes of exercise resulted in a raised FFA

level. This indicated that plasma insulin was probably not

increased in response to the oral glucose given during

exercise. Possibly the greater glucose load (94. 7 gm) in

the present study elicited a greater insulin secretion

response, therefore inhibiting FFA mobilization.

In the present study, after 90 minutes, the plasma FFA

level did show a noticeable rise to exhaustion and continued

to increase for the P and C treatments in the 30 minutes

after exercise (Figure 3). This may have occurred since the

effect of the last carbohydrate ingestion (40 minutes into

exercise) was diminished by this time. Rodahl et al.

(1964) showed that when 84 gm of glucose was given during

exercise, there was a temporary decrease, followed by a

rapid increase in FFA after the effect of insulin

diminished.

In conclusion, in spite of the achieved and desired

increase in serum FFA levels during exercise after MCT oil

ingestion in comparison to the other treatments this

treatment is not recommended in the quantities used in this

study for the athlete because of its tendency to cause

gastrointestinal distress in some individuals. In agreement

with other studies, Polycose tended to enhance exercise

performance, though not significantly, particularly delaying

49

a drop in serum glucose. Al though the combination of MCT

oil and Polycose would theoretically enhance endurance

performance due to an increased supply of both FFA and

glucose

support

available for muscular metabolism, no evidence to

this dietary strategy was found in this

investigation.

REFERENCES

Ahlborg, G. and P. Felig. "Influence of glucose ingestion on fuel; hormone response during prolonged exercise." Journal of Applied Physiology, 1976, (~), 683-688.

Bergstrom, Jonas, M.D., & Eric Hultman , M.D. for Maximal Sports Performance." Journal Medical Association, 1972, (~), 999-1007.

"Nutrition of American

Costill, David, Kenneth Sparks, Robert Gregor, & Craig Turner. "Muscle glycogen utilization during exhaustive running." Journal of Applied Physiology, 1971, (.;!), 353-356.

Costill, David, Alice Bennett, George Branam, and Duane Eddy. "Glucose ingestion at rest and during prolonged exercise." Journal of Applied Physiology, 1973, 34(.§.), 764-769.

Costill, David, E. Coyle, G. Dalsky, W. Evans, W. Fink, and D. Hoopes. "Effects of elevated plasma FFA and insulin on muscle glycogen useage during exercise." Journal of Applied Physiology: Respiration Environment Exercise Physiology, 1977, 43(1), 695-699.

Costill, David, G. Dalsky, and W. Fink. caffeine ingestion on metabolism performance." Medicine and Science in 10(.;!) I 155-158.

"Effects of and exercise Sports, 1978,

Duncombe, W. G. "The colorimetric micro-determination of nonesterified fatty acids in plasma." Clinic a Chimica Acta, 1964, ~' 122-125.

Ford tr an, J. S. and B. Sal tin. "Gastric emptying and intestinal absorption during prolonged severe exercise." Journal of Applied Physiology, 1967, 23(.;!), 331-335.

Greenberger, Norton, M.D., and Thomas Skillman, M.D. "Medium Chain Triglycerides" Physiologic considerations and clinical implicatiions." The New England Journal of Medicine, 1969, 280(19), 1045-1058.

Hickson, R.C., M.J. Rennie, R.K. Conlee, W.W. Winder, and J.O. Hollosky. "Effects of increased plasma fatty acids on glycogen utilization and endurance." Journal of Applied Physiology: Respiration Environment Exercise Physiology, 1977, 43(~), 829-833.

Holt, Peter R. M.D. "Medium -Chain Triglycerides: Auseful adjunct in nutritional therapy." Gastroenterology, 1967, 53(.§_), 961-966.

50

51

Issekutz, B., .Jr., N.C. Birkhead, and K. Rodahl. "Effect of diet on work metabolii::;m." Journal of Nutrition, 1963, 79, 109-115.

Ivy, J.L., D.L. Costill, "Influence of caffeine endurance performance." 1979, 11(!), 6-11.

W.FJ. Fink, and R.W. Lower. and carbohydrate feedings on

Medicine and Science in Sports,

Ivy, .J.L., D.L. Costill, W.J. Fink, and E. Maglischo. "Contribution of medium and long chain triglyceride intake to energy metabolism during prolonged exercise." International Journal of Sports Medicine, 1980, I, 15-20.

Ivy, J. L., W. Miller, V. Dover, L. Goodyear, W. Sherman, S. Farrell, & H. Williams. "Endurance improved by ingestion of a glucose polymer supplement." Medicine and Science in Sports and Exercise, 1983, (§), 466-471.

Laurell, Sigfrid and Gunnar Tibbling. determination of free fatty acids Chimica Acta, 1967, 10(!), 57-62.

"Colorimetric micro-in plasma. 11 Clinica

Miller, W.C., G.R. Bryce, & R.K. Conlee. "Adaptations to a high-fat diet that increase exercise endurance in male rats. 11 Journal of Applied Physiology: Respiration Environment Exercise Physiology, 1984, (!), 78-83.

Noma, Akio, Hiroaki Okabe, and Masami Kita. "A new colorimetric micro-determination of free fastty acids in serum." Clinica Chimica Acta, 1973, 43, 317-320.

Owen, O.E., A.P. Morgan, H.G.· Kemp, J.M. Sullivan, M.G. Herrera, G.F. Cahill. "Brain metabolism during fasting." Journal of Clinical Investigation, 1967, 46, 1589.

Rennie, Michael J., William W. Winder, and John 0. Hollosky. 11 A sparing effect of increased plasma fatty acids on muscle and liver glycogen content in the exercising rat." Biochemistry Journal, 1976, 156, 647-655.

Rodahl, K., H. I. Miller, and B. Issekutz, Jr. "Plasma free fatty acids in exercise." Journal of Applied Physiology, 1964, 19(~) 489-492.

Seiple, Robert S., Virginia Vivian, Edward Fox, & Robert Bartels. "Gastric-emptying characteri sties of two glucose polymer-electrolyte solutions." Medicine and Science in Sports And Exercise, 1983, (~), 366-369.

Tantibhedhyangkul, Phienvit, Theodore Vanitallie, M.D.

M.D., Sarni Hashim, M.D., and "Effects of ingestion of long-

52

chain and medium-chain triglycerides on glucose tolerance in man." Diabetes, 1967, 16, 796-799.

53

Table 1. Physical Characteristics of Subjects Prior to Initial Endurance Testing.

Subject Ht Wt Age miles Max V0 2 at 70% V02 ( cm) (kg) (years) per wk (ml/kg) (kg/kgrn)

1 175.5 72 22 200 66.6 2.3 2 172.0 62 31 60 57.7 2.0 3 178.0 84 28 165 56.3 2.3 4 178.0 70 30 50 59.4 2.0 5 178.0 71 22 100 54.0 2.0 6 179.0 67 22 75 69.0 2.2 7 178.0 67 23 175 64.3 2.2

(miles per wk= average biked)

Table 2. Statistical summary of Analysis of Variance with Repeated Measures for FFA,· Glucose, HR, R, RPE, and V02 through minute 60 of exercise.

FFA- Glucose HR R RPE Source df MS F df MS F df MS F df MS F df MS F df

error 51 .0001? 54 276.J · 108 6J.1 90 .00077 ?5 JJ.85 90

V02 MS F

6.2 person 6 .OOJ12 18.4* 6 988.8 J.6* 6 2846.o 45.1* 6 ,01J85 17.9* 5 4.62 10.2* 6 242.4 J8.9*

trt

time trt X

time

J · .00062 J.?* J 764.7 2.8* J 126.J 2.0 J .0016J 2.1 J J,17 ?,O* J 8.2 1.J

J .00099 5,9* J 48,2 0.2 6 2421J.6 J8J.8* 5 ,001J2 1.7 5 27,22 60.J* 5 11,6 . 1.9

9 .00044 2,6* 9 1JJ.6 0 • .5 18 15,J 0.2 15 .00165 2,1* 15 o.41 0.9 15 9,7 1.6

(*indicates significantly different at alpha=0,051 df = degrees of freedom, MS= Mean Square1 F =· F value I FFA = free fatty acid I HR = heart rate I R = respiratory exchange ratio I RPE = rate of perceived exertion,) ·

V\ ;{::-

_ Table J. -Mean and:S,E. values fo1f heart ,rate imd respiratory exchange ratios during exercise.

TIM& 0 10 20 30 .. 0 50 60 10 80 90 100 110 120

Ilea rt rue ( bplli)

C 1, .... 1'9-tll 153*5 15J-t5 155•5 1, ...... 155~ 152-t6 15 .... 5 159•6 167 167 170 Cll Cl) Cl) (1) Cl) Cl) Cl) (6) (6) C" I CH CH C 1)

H 79-tll 152-t5 1511•5 151it5 156-t5 1511•5 152-tla '::;6 15S-tla 150t6 156-tla Cl) (l) Cll Cll (71 (71 (71 (51 cu (2) p 70+5 153-tll 157-tll 157-tla 158-tli 158-t5 159-t5 159-t5 161-t5 158•5 16H6 156-tl 167

Ill Cll (71 (l) Cl) (71 Cl) (61 (61 (5) cu (21 (11 HP lltJ 151t5 1511•5 156-t5 157*5 156•6 1!>7+6 156+6 15S+6 152+7 15S-tl 145 145

(7) (7) Cll (71 Cl) Cll : (71 (71 (51 cu cu (11 ( 11 Reap I ratory exct1an11• ratio

~ C ----- .87+.01 .88-t.01 .89+.02 .86+.01 .88+.01 .86-t.01 .88-t.02 .86+.02 ,92+.02 ,95

(l)• Cll Cll (l) (l) Cll ,,, (61 C la I (21 H ----- .81+.02 ,86-t,02 .89-t,02 .88-t,02 .86+,02 .86+.02 ,85+,02 .Bla+,02 ,86+.0la .84+.02 -----

(lib en (71 en (71 (71 UI (51 ( J) (21 p ----- ,81+.02 .811-t,OJ .88-t.02 .87+.02 .89+,02 ,89+,02 .87+.02 ,89+.02 .93+,02 .~+.05 .88+,06 .95

(lie Cll• Cll Cll Cll. Cll 161 (51 Clal C I CJI (11 HP ----- .91t.02 .19+.01 .88-t,01 .11+.01 .11•.01 ·,91•.01 .16•.01 .16•.oi .16+.02 .15+.02 .n+.01a .Bl

Ul•bc C11• Cl) (!) Cl) (ll (51 (5) (J) ( J) (2) ( 11

Values are 11ean1 -t S.E., va1ua1 In parentheala are the nulllber or aubjecu used to co11pute the uan. Values with the &8R1e letter are slgnlrlcantll/' dlrforent at p

Table 4. Mean and S,E. values for serum metabolites and results of one-way AliOVA during exe:r:cise.

11 .. 0 H JO ~ ,. 120 (1111 POil ---Oluca1e 111911

G ,o.i•J.' 96.ll•l. I .......... .. ... ,., 91.2•6.0 " ... ,., ... "·"*"·~ 111 111 111 111 1,1 111 111 111• " ,z.,.,., ,a.,., .• ,,. ,., ... 91. ,., •• .,., ... , --- ,, .... , .. .. ....... 111 111• 111 111 (Ill 111• 11Jcd , ....... , .. HJ.2tU.6 '°'·"·'·' IOJ.J•J,6 ....... , ... '°' "'·f*"·' "'· ..... , 111 111• Cit CJI .,. (II JI• CJl•d "' ..... ,., .. ... , .... , ..... ,.,.' ..... , .. 96 ...... , ., .... , ..... IOI. 1+7.6 111 CJI 111 Cll .... Ill en CJIIIO

Free FH&JI' aolda 1 ... 1

G ....... ., ..... , .Jl+.Ol .n•.n ., .... n ., .. . .... " 1.00+.11 111 CJI CJI CJI• ,,, Ill (JI CJI• " .Ht.OJ ...... , ... 10.12 .6'•.12 .,, .... --- 1.111+.21 .16+.II 111 111 111 CJl•lld UI CJI Ill ' ... , •. o, ....... ....... ., .... 06 ··m·· irl ,6J+. u .61+.22 111 CJI. 111 111••• CJI 111 "' ....... .Jt+.o, ...... • .. , •• 10 ....... ·f' .61+.22 .H•.11 UI 111 (JI C Jlllo (Ill C I 111 CJI•

ValuH ara eoano • I.I., v11ue1 In r•r•nt1111l1 are tl,e m•bero or 1ubJ10:t1 uHd &a o_..,. the .. ,n. Value• whh ,,,. HM loll•r ar• 1l1nlrlaantli, dlrrarent 1t pc. I, G, co11tro11 H, 11Cl1 P, 1luco11 poli,eer1 Hf, IICI • 1lucD11 poli,•r1 (ICil, ••hau11.lon.

V\

°'

57

FIGURE LEGENDS

FIG. 1. Mean time to exhaustion for treatments MCT oil

(M), Polycose (P), MCT oil with Polycose (MP), and

Control (CTR). No significant difference was

found between treatments (p < 0.05). Bar

extension lines represent S.D.

FIG.